In certain technologies, such as orthogonal frequency division multiplexing (OFDM), a communications channel between two devices is implemented through multiple subcarriers. Each subcarrier of a channel may have a different signal-to-interference-plus-noise ratio (SNR) associated with the subcarrier at a particular instant in time. Methodologies have been introduced that map the instantaneous SNR of multiple subcarriers into an effective channel SNR associated with the channel. The effective channel SNR can be used, for example, to determine a block-error probability (BLEP) for a given particular channel state. The BLEP may be used to determine an appropriate modulation and coding scheme (MCS) for use on the channel to optimize throughput of the channel. Determining an effective channel SNR is also useful in system level simulations.
It is common today to code information bits with forward error correction bits and send the data in a forward error correction (FEC) block. The effects of noise and interference may prevent a receiver from decoding an FEC block. Thus, it is necessary to periodically retransmit a FEC block. The retransmitted FEC block may be combined with the original FEC block, and if the combined FEC block cannot be properly decoded, additional FEC blocks will be requested until the FEC block can be decoded. Some retransmission technologies, such as Adaptive Hybrid Automatic Repeat Request (A-HARQ) for example, allow the modulation order of a retransmitted FEC block to differ from the modulation order used to transmit the original FEC block. It may be desirable for the transmitter to send the retransmitted FEC block at a particular SNR to increase the likelihood that the combined FEC block can be decoded. Thus, it would be helpful to determine an effective channel SNR associated with the transmission of two FEC blocks of data at different modulation orders. However, the known methodologies for determining an effective channel SNR cannot determine an effective channel SNR associated with transmissions at different modulation orders. With increased interest in the use of A-HARQ for emerging telecommunication technologies, there is a need for a mechanism for determining an effective channel SNR associated with data transmitted at different modulation orders.